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8 mar 2021 · select jobs, nvl(salary, 0) as salary from your_table Or COALESCE. select jobs, coalesce(salary, 0) as salary from your_table Or DECODE. select jobs, decode(salary, null, 0, salary) as salary from your_table Or CASE. select jobs, case when salary is null then 0 else salary end as salary from your_table
4 sty 2011 · NULL means absence of value (i.e. there is no value), while empty string means there is a string value of zero length. For example, say you have a table to store a person' data and it contains a Gender column. You can save the values as 'Male' or 'Female'.
Use a null when the actual value is not known or when a value would not be meaningful. Oracle Database treats a character value with a length of zero as null. However, do not use null to represent a numeric value of zero, because they are not equivalent.
To concatenate an expression that might be null, use the NVL function to explicitly convert the expression to a zero-length string. Example This example creates a table with both CHAR and VARCHAR2 columns, inserts values both with and without trailing blanks, and then selects these values, concatenating them.
DROP TABLE null_test_tab; CREATE TABLE null_test_tab ( id NUMBER, col1 VARCHAR2(10), col2 VARCHAR2(10), col3 VARCHAR2(10), col4 VARCHAR2(10) ); INSERT INTO null_test_tab values (1, 'ONE', 'TWO', 'THREE', 'FOUR'); INSERT INTO null_test_tab values (2, NULL, 'TWO', 'THREE', 'FOUR'); INSERT INTO null_test_tab values (3, NULL, NULL, 'THREE', 'FOUR ...
"Strings of Zero Length Not Equivalent To NULL". "A string of zero length ('') is not equivalent to a NULL value. According to the ANSI SQL 1992 Transitional standard, a zero-length or empty string is not the same as NULL. Ensure that applications do not treat empty strings and NULL values equivalently."
The Oracle NVL() function allows you to replace null with a more meaningful alternative in the results of a query. The following shows the syntax of the NVL() function: NVL(e1, e2) Code language: SQL (Structured Query Language) ( sql )
